Table 2 Screw placement quality with the modified Gertzbein–Robbins classification.

From: The accuracy of cortical bone trajectory screw placement guided by spinous process clamp hardware in lumbar spinal surgery: a retrospective study

Grade

Total (n = 128)

FH group (n = 64)

SPC guide group (n = 64)

χ2/T-value

P value

A (n %)

58 (45.3%)

23 (35.9%)

35 (54.7%)

4.540

0.033*

B (n %)

52 (40.6%)

28 (40.6%)

24 (37.5%)

0.518

0.472

A + B (n %)

110 (84.9%)

51 (79.7%)

59 (92.2%)

4.137

0.042*

C (n %)

11 (8.6%)

7 (10.9%)

4 (6.3%)

0.895

0.344

D# (n %)

5 (3.9%)

4 (6.3%)

1 (1.6%)

–

0.365

E# (n %)

2 (3.1%)

2 (3.1%)

0 (0.0%)

–

0.154

C + D + E (n %)

18 (14.1%)

13 (20.3%)

5 (7.8%)

4.137

0.042*

FJV (n %)

12 (9.4%)

10 (15.6%)

2 (3.1%)

4.506

0.034*

Lateral angle (°)

8.5 ± 3.2

6.4 ± 3.1

10.1 ± 2.0

− 3.972

 > 0.001*

Cranial angle (°)

25.3 ± 5.5

23.0 ± 4.4

27.7 ± 5.5

− 2.716

0.011*

  1. FJV, Facet joint violation, NA, Not available. Values are expressed as the mean ± standard deviation or number.
  2. *P < 0.05, as compared with the two groups value.
  3. #The total number of cases in this study was < 40 or theoretical frequency < 1, so the results of Fisher's Exact Test were used.
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